Transfer elements and method of making same

ABSTRACT

Pressure-sensitive transfer elements of the squeezeout type which are rendered cleaner to the touch and resistant to producing typewriter roller marks on the copy sheet by covering the ink-releasing surface of such transfer elements with a very thin porous layer of thermoplastic resin particles which are fused to each other and to the ink layer to provide an inkpermeable protective layer over the ink layer.

United States Patent Inventor Douglas A. Newman Glen Cove, NY.

Sept. 25, 1967 Nov. 2, 1971 Columbia Ribbon and Carbon ManufacturingCo., Inc.

Glen Cove, N.Y.

Appl. No. Filed Patented Assignee TRANSFER ELEMENTS AND METHOD OF MAKINGSAME 10 Claims, 2 Drawing Figs.

US. Cl 117/21, 117/36.4,117/36.2,l17/138.8,117/29 lnt.Cl 841m 5/10 Fieldof Search l17/36.4, 21

Primary Examiner-Murray Katz Attorney-Johnson & Kline ABSTRACT:Pressure-sensitive transfer elements of the squeezeout type which arerendered cleaner to the touch and resistant to producing typewriterroller marks on the copy sheet by covering the ink-releasing surface ofsuch transfer elements with a very thin porous layer of thermoplasticresin particles which are fused to each other and to the ink layer toprovide an ink-permeable protective layer over the ink layer.

TRANSFER ELEMENTS'AND METHOD OF MAKING SAME The present inventionrelates to the field of the so-called squeezeout" carbon papers andribbons on which the transfer layer comprises a microporousnontransferable resinous structure containing within the pores thereof apressure-exudable ink comprising an oily vehicleand imaging matter. Suchtransfer elements are illustratedjbyUS. Pats. Nos. 2,820,717; 9,944,0373,037,879 and 3,117,018, among others.

Such known transfer elements have been exceptionallysuccessful primarilybecause of their reusability. The resinous binder is not transferableand its porosity permits the flowable ink to migrate and replenish areasfrom which ink has been transferred. However, while the ease offlowability has this advantage, it has the disadvantage that some amountof the ink can exude to the copy sheet with which it is superposed whenthe sheets are inserted into a-typewriter or similar business machinehaving rollers between which the sheets are compressed.

it is possible to avoid or at least diminishthis undesirable offsettingby formulating the ink layer from harder, less pressure-compressibleresins or resin mixtures or by using semisolid ink vehicles. However,this reduces the pressure sensitivity of the ink layer so that the typedcopies are not as dense as desired, particularly when interleaved carbonpapers are used to produce a number of copies at one typing.

it is the principal object of the present invention to provide improvedsqueezeout-type transferelements which are clean to the touch and do notproduce roller marks on the copy sheet and which retain a high degree ofpressure sensitivity so as to produce images of high intensity even wheninterleaved to produce several copies at one typing.

Other objects and advantages of this invention will be clear to thoseskilled in the art in the light of the present disclosure, including thedrawings, in which:

FIG. 1 is a diagrammatic illustration of the ing the presentsupercoatings; and

FIG. 2 is a diagrammatic cross section, to' an enlarged scale, of atransfer element produced according to the present invention.

The objects and advantages of the present invention are attained bycovering the ink-releasing surface of a squeezeouttype resinous inklayer with a'thin coating consisting essentially of thermoplastic resinparticles, preferably dispersed in a volatile vehicle which isthereafter evaporated, and then approcess of apply- ,plying sufficientheat to soften the surface of the resin particles, without melting theparticles themselves, to cause the particles to adhereto particles incontact therewith and to adhere to the surface of the ink layer, if incontact therewith, and thereafter cooling the particulate coating as aporous, inkpermeable layer over the ink layer.

it should be made clear that the present particulate coating It isdifi'icult to say with certainty how the present wash coats prevent theformation of roller markswithout reducing the imaging pressuresensitivity of squeezeout-type layers. The present porous particulatecoatings form a microporous screen on the ink-releasing surface due tothe fact that the particulate coating contains interstices or voids vbetween fused particles which permit inkto be forced therethrough underthe effect of imaging pressure. The interstices are so small, ac-

tually microporous, and the particulate supercoating has such athickness above the surface of the ink layer that the pressure exertedby typewriter rollers'or during handling is insufficient to cause theink to penetrate through the supercoating whereas imaging pressures suchas typing pressures are suffcient to transfer the ink through to a copysheet. I

The preferred particulate coating compositions of the present inventionconsist essentiallyof dispersions of from about 5 percent up to about 50percent by weight of a thermoplastic resin in water or a volatileorganic vehicle which is not a solvent for the resin particles or forthe resinous binder 'of the ink layer. Particulate vinyl resins ingeneral are suitable and include polyvinyl chloride, polyvinyl acetate,vinyl chloride copolymers with vinylacetate, 'polystyrene, polyvinylbutyral, acrylic acid and ester polymers and copolymers such aspolymethyl methacrylate, methyl methacrylateethyl acrylate copolymersand the like. Other thermoplastic resins of natural and synthetic originare also suitable such as rubber latices, copal, colophony,polyethylene, polypropylene, polycarbonates, cellulose acetate, ethylcellulose and other thermoplastics. g

' Aqueous emulsions or latices of these resins are preferred. Suitablevolatile organic vehicles are toluene, xylene, naphtha,

butanol, propanol, ethylene glycol and similar nonsolvents dependingupon the solubility properties of the resin particles of thesupercoating and the resin binder of the ink layer. Of course smallamounts of compatible plasticizers, fillers, colorants or the like maybe included in the resin particles provided that such additives do notinterfere with the porosity and intended performance of thesupercoating.

The particle size of the resin used may be varied over a relatively widerange depending upon the degree of pressure sensitivity of theink-releasing layerand the degree of pressure sensitivity desired in thefinal transfer element. Some elements aresubjected to heavy imagingpressures, such as typewriter carbons and ribbons and printing machineribbons, while others'are used under lighter pressures, such as pencilcarbons and roller-pressure carbons. in general, the large particlesizes, from about 150 mesh up to about l00 mesh per inch, provide largerpores and freer ink'esca'pe and are preferred for the latter uses.Smaller particle sizes provide smaller but more numerous pores andtherefore produce more uniform copy and are preferred for the formeruses where the degree of imaging pressure is sufiicient to insureadequate ink exudation. In this regard, particle sizes in the range offrom 1000 does not form a continuous film or layer over the ink layer.

This effect is to be avoided since such a continuous film seals the inklayer and prevents the ink layer from exuding ink under the effect ofimaging pressure. Care mustbe taken in heating the particulate coatingso that the resin particles are fused together at only their contactpoints whereby the interstices between contacting particles are retainedunsealed.

It has also been found that the wash coating must be free of oils orother oleaginous materials which are incompatible with the resinparticles of the wash coating since such materials separate from theresin particles to form unpigmented droplets through which the ink ofthe transfer layer must be transmitted. This results in a dilution ofthe ink and a reduction in its tone or imaging strength, and a lack ofuniformity of imaging strength over the surface of the transfer element.The

' inclusion of pigment in such oil phase overcomes this problem butresults in a transfer element which is dirty to the touch and producesroller marks during use. However, it should be mesh up to about 200 meshper inch are suitable, with sizes ranging from 300 to 600 mesh beingpreferred. a

Similarly the thickness of the supercoating may be varied depending onthe degree of pressure sensitivity desired and the degree of cleanlinessrequired. Generally the thickness will vary from a single layer ofparticles, each adhered to the surface of the ink layer, to a multilayer of particles adhered to one another. Thicknesses ranging as low as0.0005 inch and up to 0.01 inch are possible, the preferred range beingfrom about 0.002 to 0.005 inch.

According to the preferred embodiment, the particles are applied to thesurface of the ink layer in a volatile vehicle and spread by means of adoctor blade to form a wet film which, after evaporation of the vehicle,has the desired thickness.

The present supercoatings may be applied in the manner illustrated byFIG. 1 of the drawing when using a volatile vehicle. The web of transferelement 10 is expended from supply 'roll 11 over idler roller l2'andagainst application roller 13 which is immersed in vat 14 containing asupply of the supercoating dispersion. The dispersion is applied to theunderside of the web over the squeezeout ink-releasing layer and isspread to the desired thickness by means of doctor blade 15. The wet webthen passes under idler roller 16 and over heat lamps 17 which causeevaporation of the volatile solvent and drying of the thin resinstructure. The web then passes through oven 18 to cause surface fusionof the resin particles and then under idler roller 19 and onto takeuproll 20.

The structure of the final transfer element is as illustrated in FIG. 2of the drawings. The transfer element has a flexible foundation 21carrying a microporous squeezeout-type inkreleasing layer 22 and a thinnontransferable particulate fused resin supercoating 23 over saidink-releasing layer. The inkreleasing layer comprises a nontransferablemicroporous resinous structure 24 containing droplets 25 ofpressure-transferable oily ink within the pores thereof. Thesupercoating consists of discrete resin particles 26 bonded to eachother and forming between each other interstices or voids 27 throughwhich the liquid ink droplets 25 can be exuded under imaging pressure.Thus while imaging pressure is sufficient to exude the oily ink droplets25 to a copy sheet, the lesser pressure exerted by a typewriter rolleror the like is not sufficient to cause the oily ink to exude beyond thesurface of the particulate supercoating 23.

it should be understood that the present particulate supercoatings mayalso be applied as a dry resin powder without any liquid vehicle. Thepowder may be brushed on or attracted by a static charge placed on theink layer or merely deposited thereon by gravity as a layer of uniformthin caliper. Thereafter the powder particles are heated to causebonding without complete melting as discussed supra, to produce thedesired results.

The following example illustrates the production of one type of transferelement according to the present invention and should not be consideredlimitative.

A film web of -mil polyethylene terephthalate polyester (Mylar) is firstcoated with a thin layer of polyvinylidene chloride (Saran) dissolved inmethyl ethyl ketone to provide a receptive undercoating having athickness of about 0.1 mil. After evaporation of the solvent, theundercoating is coated with the following ink composition:

The applied ink composition is dried at elevated temperatures to form amicroporous ink layer having a thickness of about 0.6 mil.

As shown in FIG. 1, the transfer element formed as above is passed incontact with an application roller 13 so that the ink layer is providedwith a thin layer of the resin particle coating composition in vat 14which is a 40 percent dispersion of polyvinyl chloride (600 mesh perinch) in xylene as the nonsolvent vehicle. Doctor blade spreads the washcoating to a wet thickness of about 30 points (0.003 inch). Thereafterthe transfer element is heated to evaporate the xylene and leave thedried polyvinyl chloride particle structure having a thickness of about1.2 mil (0.0012 inch). The polyvinyl chloride coating is next heated inoven 18 to a temperature of about 350 F. to soften the particles andcause them to adhere to one another and to the surface of the ink layer.

The finished film web is cooled and collected on takeup roll for cuttinginto sheets or ribbons of the desired dimensions.

The present invention is principally concerned with the production oftransfer sheets for typewriter use and transfer strips or wide ribbonsfor other business machine use.

While pigments such as the carbon blacks, magnetic iron oxides,particulate dyestuffs and toned pigments having dyes of the desiredcolors precipitated and absorbed on the surface of porous pigments arethe preferred coloring materials, other coloring materials are alsouseful including the substantially colorless color-forming reactivechemicals which form colored reaction products on contact with othercolorless coreactive chemicals present on the copy sheet surface.

It should be understood that the present invention also applies to theproduction of self-supporting ink-releasing microporous layers which areformed on a casting surface and thereafter tripped therefrom in knownmanner. Such transfer elements are preferably coated on both surfaceswith the present particulate supercoatings for complete coverage.

Variations and modifications may be made within the scope of the claims,and portions of the improvement may be used without others.

lclaim:

l. The process of producing reusable pressure-sensitive transferelements of the squeezeout type which are clean to the touch andresistant to exuding ink under the effects of pressure less than imagingpressure which comprises:

a. coating an impervious flexible plastic film of polyethyleneterephthalate polyester with a thin layer of vinyl resin to provide areceptive undercoating thereon;

b. applying to said undercoating a pressure-sensitive squeezeout-typeink layer comprising a pressure nontransferable microporous structure ofsynthetic thermoplastic resin containing within the pores thereof apressure-exudable ink comprising an oily vehicle and coloring matter;

c. providing over the ink-releasing surface of said ink layer a thinporous layer of small, relatively uniform, discrete, dry particles ofthermoplastic resin;

. applying sufficient heat to soften the surface of said dry particleswithout complete melting thereof to cause the particles to adhere toparticles in contact therewith without destroying the porosity of thelayer and to cause the porous layer to bond to the surface of the inklayer as a layer having a thickness of from about 0.0005 inch up toabout 0.01 inch; and

e. cooling the layer as an ink-permeable supercoating which is nottransferable from the ink layer under the effects of imaging pressureduring repeated reuse of the transfer element.

2. The process of claim 1 in which the resin particles are provided overthe ink-releasing surface by applying them as a dispersion in a volatilevehicle which is a nonsolvent for the resin of the ink layer, and heatis applied to evaporate said vehicle and form said discrete, dryparticles.

3. The process of claim 2 in which the dispersion of resin particles isapplied in a thickness to provide a dried resin layer having a thicknessof from about 0.0005 inch to 0.005 inch.

4. The process of claim 1 in which the synthetic resin of the ink layerand the resin particles comprise vinyl resins.

5. The process of claim 1 in which the resin particles are provided overthe ink-releasing surface by applying them as discrete, dry particles.

6. A reusable pressure-sensitive transfer element of the squeezeouttype, which is clean to the touch and resistant to exuding ink under theeffects of pressure less than imaging pressure, which comprises animpervious flexible plastic film of polyethylene terephthalate polyesterhaving on one surface thereof a thin receptive undercoating of vinylresin and having on said undercoating a pressure-sensitivesqueezeout-type ink layer comprising a pressure nontransferablemicroporous structure of synthetic thermoplastic resin containing withinthe pores thereof a pressure-exudable ink comprising an oily vehicle andcoloring matter, and having heat-fused to the surface of said ink layera thin porous fused particulate layer having a thickness of from about0.0005 inch to about 0.01 inch consisting essentially of small,relatively uniform particles of thermoplastic resin which have beenheated sufficiently to cause them to heat-fuse to particles in contacttherewith without destroying the porosity of the layer and sufficientlyto heat-fuse them to the surface of the ink layer whereby they are nottransferable from the ink layer under the effects of imaging pressureduring repeated reuse of the transfer element.

7. A transfer element according to claim 6 in which the synthetic resinof the ink layer and the thermoplastic resin of the particulate layercomprise vinyl resins.

8. A transfer element according to claim 6 in which the par-

2. The process of claim 1 in which the resin particles are provided overthe ink-releasing surface by applying them as a dispersion in a volatilevehicle which is a nonsolvent for the resin of the ink layer, and heatis applied to evaporate said vehicle and form said discrete, dryparticles.
 3. The process of claim 2 in which the dispersion of resinparticles is applied in a thickness to provide a dried resin layerhaving a thickness of from about 0.0005 inch to 0.005 inch.
 4. Theprocess of claim 1 in which the synthetic resin of the ink layer and theresin particles comprise vinyl resins.
 5. The process of claim 1 inwhich the resin particles are provided over the ink-releasing surface byapplying them as discrete, dry particles.
 6. A reusablepressure-sensitive transfer element of the squeezeout type, which isclean to the touch and resistant to exuding ink under the effects ofpressure less than imaging pressure, which comprises an imperviousflexible plastic film of polyethylene terephthalate polyester having onone surface thereof a thin receptive undercoating of vinyl resin andhaving on said undercoating a pressure-sensitive squeezeout-type inklayer comprising a pressure nontransferable microporous structure ofsynthetic thermoplastic resin containing within the pores thereof apressure-exudable ink comprising an oily vehicle and coloring matter,and having heat-fused to the surface of said ink layer a thin porousfused particulate layer having a thickness of from about 0.0005 inch toabout 0.01 inch consisting essentially of small, relatively uniformparticles of thermoplastic resin which have been heated sufficiently tocause them to heat-fuse to particles in contact therewith withoutdestroying the porosity of the layer and sufficiently to heat-fuse themto the surface of the ink layer whereby they are not transferable fromthe ink layer under the effects of imaging pressure during repeatedreuse of the transfer element.
 7. A transfer element according to claim6 in which the synthetic resin of the ink layer and the thermoplasticresin of the particulate layer comprise vinyl resins.
 8. A transferelement according to claim 6 in which the particulate layer ofthermoplastic resin comprises polyvinyl chloride.
 9. A transfer elementaccording to claim 6 in which the particulate layer of thermoplasticresin has a thickness of from about 0.0005 inch to 0.01 inch.
 10. Atransfer element according to claim 9 in which the particulate layer hasa thickness of from about 0.002 inch to 0.005 inch.